Experimental Study of Full Coverage Film Cooling Effectiveness for a Turbine Blade With Compound Shaped Holes

The film coverage of the turbine blade surface is determined by all the film cooling structures. There are already numerous literatures studying the influence of cooling structure parameters on cooling effectiveness. However, the direct study of full-coverage film cooling is relatively rare, especially for the related research of turbine rotor blades. In this paper, pressure sensitive paint (PSP) measurement technique is used to carry out experiments under different turbulence intensities and mass flux ratios, and the distribution of the film cooling effectiveness on the entire surface of the turbine blades is studied in detail. This article has studied a basic turbine blade and an improved turbine blade, the film cooling holes’ position distribution on the improved blade is the same as the basic blade, but the film cooling hole shape on the suction surface and the pressure surface is changed from cylindrical holes to laid-back fan-shaped holes. Both blades have 5 rows of cylindrical holes at the leading edge, and 4 rows of film cooling holes on the suction surface and the pressure surface. The leading edge, suction surface, and pressure surface have their own coolant inlet cavities, This kind of design is not only close to the actual working conditions in the flow distribution, but also convenient to eliminate the mutual interference caused by the uneven flow distribution between the pressure surface and the suction surface, so as to facilitate the independent analysis of the pressure surface and the suction surface.

In this paper, the film cooling effectiveness of two kinds of turbine blades under different turbulence intensities and mass flux ratios are studied. The results show that the average cooling effectiveness of the improved blade is much better than that of the basic blade. The laid-back fan-shaped hole rows improve the cooling effectiveness of the suction surface by 60% to 100% and 50% to 120% on the pressure surface. The increase of turbulence intensity will reduce the cooling effectiveness of blade surface; however, the effect of turbulence intensity becomes weaker with the increase of mass flux ratio. Compared with the multi rows of cylindrical holes, the cooling effectiveness of the laid-back fan-shaped holes is more affected by the turbulence intensity under the small mass flow ratio.